// Evaluate result=leftFactor*left + productFactor*this^transpose*rightFactor
protected override Vector <float> MultiplyAndAddAsLeftFactorCore(
float leftFactor,
Vector <float> left,
float productFactor,
TransposeOperation transpose,
Vector <float> rightFactor,
Vector <float> result)
{
// The matrix has 1+4*alpha on the main diagonal,
// and -alpha on the 1st and nth sub and superdiagonal.
// result may be null. Using MultiplyInto will create
// a vector if necessary and will return it.
result = Vector.MultiplyInto(leftFactor, left, result);
// Diagonal
result.AddScaledInPlace(1.0f + 4.0f * alpha, rightFactor);
// Superdiagonal 1
result.GetSlice(0, N - 2, 1, Intent.WritableView)
.AddScaledInPlace(-alpha, rightFactor.GetSlice(1, N - 1));
// Superdiagonal size
result.GetSlice(0, N - n - 1, 1, Intent.WritableView)
.AddScaledInPlace(-alpha, rightFactor.GetSlice(n, N - 1));
// Subdiagonal 1
result.GetSlice(1, N - 1, 1, Intent.WritableView)
.AddScaledInPlace(-alpha, rightFactor.GetSlice(0, N - 2));
// Subdiagonal size
result.GetSlice(n, N - 1, 1, Intent.WritableView)
.AddScaledInPlace(-alpha, rightFactor.GetSlice(0, N - n - 1));
return(result);
}
